HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Free Full Text (PDF) Free All Versions of this Article: 97/4/1431    most recent 00277.2004v1 Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (13) Citing Articles via Google Scholar Google Scholar Articles by Bouairi, E. Articles by Mendelowitz, D. Search for Related Content PubMed PubMed Citation Articles by Bouairi, E. Articles by Mendelowitz, D.

Respiratory sinus arrhythmia in freely moving and anesthetized rats

¹Department of Pharmacology and Physiology, George Washington University, Washington, District of Columbia 20037; and ²Department of Physiology and Pharmacology, Oregon Health and Science University Portland, Oregon 97239-3098

Submitted 12 March 2004 ; accepted in final form 18 May 2004

Heart rate increases during inspiration and slows during postinspiration; this respiratory sinus arrhythmia helps match pulmonary blood flow to lung inflation and maintain an appropriate diffusion gradient of oxygen in the lungs. This cardiorespiratory pattern is found in neonatal and adult humans, baboons, dogs, rabbits, and seals. Respiratory sinus arrhythmia occurs mainly due to inhibition of cardioinhibitory parasympathetic cardiac vagal neurons during inspiration. Surprisingly, however, a recent study in anesthetized rats paradoxically found an enhancement of cardiac vagal activity during inspiration, suggesting that rats have an inverted respiratory sinus arrhythmia (Rentero N, Cividjian A, Trevaks D, Pequignot JM, Quintin L, and McAllen RM. Am J Physiol Regul Integr Comp Physiol 283: R1327–R1334, 2002). To address this controversy, this study examined respiratory sinus arrhythmia in conscious freely moving rats and tested whether the commonly used experimental anesthetics urethane, pentobarbital sodium, or ketamine-xylazine alter respiratory sinus arrhythmia. Heart rate significantly increased 21 beats/min during inspiration in conscious rats, a pattern similar to the respiratory sinus arrhythmia that occurs in other species. However, anesthetics altered normal respiratory sinus arrhythmia. Ketamine-xylazine (87 mg/kg and 13 mg/kg) depressed and pentobarbital sodium (60 mg/kg) abolished normal respiratory sinus arrhythmia. Urethane (1 g/kg) inverted the cardiorespiratory pattern so that heart rate significantly decreased during inspiration. Our study demonstrates that heart rate normally increases during inspiration in conscious, freely moving rats, similar to the respiratory sinus arrhythmia pattern that occurs in other species but that this pattern is disrupted in the presence of general anesthetics, including inversion in the case of urethane. The presence and consequences of anesthetics need to be considered in studying the parasympathetic control of heart rate.

heart rate variability; cardiac; vagal; parasympathetic; ambiguus

This article has been cited by other articles:

				J. B. Samora, J. C. Frisbee, and M. A. Boegehold Increased myogenic responsiveness of skeletal muscle arterioles with juvenile growth Am J Physiol Heart Circ Physiol, May 1, 2008; 294(5): H2344 - H2351. [Abstract] [Full Text] [PDF]

				D. Accorsi-Mendonca, R. M. Leao, J. F. Aguiar, W. A. Varanda, and B. H. Machado Urethane inhibits the GABAergic neurotransmission in the nucleus of the solitary tract of rat brain stem slices Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R396 - R402. [Abstract] [Full Text] [PDF]

				J. R. Padley, D. H. Overstreet, P. M. Pilowsky, and A. K. Goodchild Impaired cardiac and sympathetic autonomic control in rats differing in acetylcholine receptor sensitivity Am J Physiol Heart Circ Physiol, November 1, 2005; 289(5): H1985 - H1992. [Abstract] [Full Text] [PDF]